1. Field of the Invention
The present invention relates to a driver circuit suitable for use as an output stage of logic circuits formed in Large Scale Integrated Circuits (LSI).
2. Background Art
Some logic circuits formed in LSIs are provided with driver circuits for the purpose of driving a large capacitive load at the output stage. FIG. 4 shows such a driver circuit 50 and an overview of the output side.
The driver circuit shown in FIG. 4 is connected to the PMOS-Tr (P-channel Metal Oxide Semiconductor field effect Transistor) 52 and NMOS-Tr (N-channel Metal Oxide Semiconductor field effect Transistor) 53, and the output end of the driver circuit is connected to the gate terminal of the PMOS-Tr 52 and the gate terminal of the NMOS-Tr 53, and the driver circuit 50 is provided with an inverter 51 which is a pre-driver for driving the PMOS-Tr 52 and the NMOS-Tr 53.
The output terminal 74 of the driver circuit 50 is connected with a logic circuit 62 having a gate 63 as an inputting stage for receiving the signals from the driver circuit 50. This output terminal 74 is also to be connected to capacitive load 61 such as a floating capacity which is carried on a wiring to the logic circuit 62 and an input capacity of the gate 63.
When an "H" (high voltage level) signal is input at the data input end 71 of the driver circuit 50, the driver circuit 50 charges the large capacitive load 61 connected to the output terminal 74 of the driver circuit 50. When, in contrast, the "L" (low voltage level) signal is input at the data input end 71, the driver circuit 50 discharges the large capacitive load 61.
However, problems arise in the driving circuit structure shown in FIG. 4 as follows. The first problem is that the conventional driving circuit requires a high driving current and its operating speed is low, since the load capacity is fully oscillated in a voltage range corresponding to the driving voltage.
The second problem is the wide gate width, since it is required for the PMOS-Tr 52 and the NMOS-TR 53 to have the ability to output large electric currents. Consequently, it is likely that noise components will be carried on wiring to the electric source or wiring to the ground. The third problem is that the penetration current becomes large during load driving for the same reasons as described above.
It is therefore the object of the present invention to provide a driver circuit which does not require a high output current even if a logic circuit with a large capacitive component is connected as a load, and which is capable of high speed operation or of reduced noise.